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Small performance optimization and size reduction in sqlite3BtreeDelete().

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FossilOrigin-Name: da0af4dd9ba4180a16543fac1549fd4ccecdc66dcf6d275f77de21fd80708882
This commit is contained in:
drh
2022-01-02 14:55:43 +00:00
parent 44a5c0257f
commit 7e17a3abbe
3 changed files with 31 additions and 24 deletions
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41
src/btree.c
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@@ -9229,14 +9229,13 @@ int sqlite3BtreeTransferRow(BtCursor *pDest, BtCursor *pSrc, i64 iKey){
int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
Btree *p = pCur->pBtree;
BtShared *pBt = p->pBt;
int rc; /* Return code */
MemPage *pPage; /* Page to delete cell from */
unsigned char *pCell; /* Pointer to cell to delete */
int iCellIdx; /* Index of cell to delete */
int iCellDepth; /* Depth of node containing pCell */
CellInfo info; /* Size of the cell being deleted */
int bSkipnext = 0; /* Leaf cursor in SKIPNEXT state */
u8 bPreserve = flags & BTREE_SAVEPOSITION; /* Keep cursor valid */
int rc; /* Return code */
MemPage *pPage; /* Page to delete cell from */
unsigned char *pCell; /* Pointer to cell to delete */
int iCellIdx; /* Index of cell to delete */
int iCellDepth; /* Depth of node containing pCell */
CellInfo info; /* Size of the cell being deleted */
u8 bPreserve; /* Keep cursor valid. 2 for CURSOR_SKIPNEXT */
assert( cursorOwnsBtShared(pCur) );
assert( pBt->inTransaction==TRANS_WRITE );
@@ -9255,23 +9254,31 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
iCellDepth = pCur->iPage;
iCellIdx = pCur->ix;
pPage = pCur->pPage;
if( pPage->nCell<=iCellIdx ){
return SQLITE_CORRUPT_BKPT;
}
pCell = findCell(pPage, iCellIdx);
if( pPage->nFree<0 && btreeComputeFreeSpace(pPage) ){
return SQLITE_CORRUPT_BKPT;
}
if( pPage->nCell<=iCellIdx ){
return SQLITE_CORRUPT_BKPT;
}
/* If the bPreserve flag is set to true, then the cursor position must
/* If the BTREE_SAVEPOSITION bit is on, then the cursor position must
** be preserved following this delete operation. If the current delete
** will cause a b-tree rebalance, then this is done by saving the cursor
** key and leaving the cursor in CURSOR_REQUIRESEEK state before
** returning.
**
** Or, if the current delete will not cause a rebalance, then the cursor
** If the current delete will not cause a rebalance, then the cursor
** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
** before or after the deleted entry. In this case set bSkipnext to true. */
** before or after the deleted entry.
**
** The bPreserve value records which path is required:
**
** bPreserve==0 Not necessary to save the cursor position
** bPreserve==1 Use CURSOR_REQUIRESEEK to save the cursor position
** bPreserve==2 Cursor won't move. Set CURSOR_SKIPNEXT.
*/
bPreserve = (flags & BTREE_SAVEPOSITION)!=0;
if( bPreserve ){
if( !pPage->leaf
|| (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
@@ -9282,7 +9289,7 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
rc = saveCursorKey(pCur);
if( rc ) return rc;
}else{
bSkipnext = 1;
bPreserve = 2;
}
}
@@ -9382,8 +9389,8 @@ int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
}
if( rc==SQLITE_OK ){
if( bSkipnext ){
assert( bPreserve && (pCur->iPage==iCellDepth || CORRUPT_DB) );
if( bPreserve>1 ){
assert( (pCur->iPage==iCellDepth || CORRUPT_DB) );
assert( pPage==pCur->pPage || CORRUPT_DB );
assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
pCur->eState = CURSOR_SKIPNEXT;